Genetic Connectivity, Adaptation, and Phenotypic Plasticity of Corals and Anemones Under Thermal Stress

Hanny Rivera, Ph.D., 2019Ann Tarrant, Advisor

Under global climate change, our oceans are warming at an unprecedented rate. This thesis aims to understand how corals and anemones respond to changing temperatures across different timescales. I explore three case studies of thermal stress response. I begin with corals from the central Pacific, where the El Niño Southern Oscillation repeatedly causes high temperatures and mortality. I find El Niño-impacted reefs maintain genetic diversity indicating recruitment from nearby reefs may occur. Yet, they show significant genetic differentiation from farther areas, suggesting this dispersal may be limited. Next, I investigate genetic connectivity and adaptation to chronically high temperatures across a natural gradient in the Palau. Combining genetic data and historical growth records, I find that Palau’s warmest reefs harbor unique genetic subpopulations with a genetic basis for higher thermal tolerance. Lastly, I explore if parents can modulate parental effects to increase the thermal tolerance of offspring, using the anemone Nematostella vectensis. I find parents exposed to increased temperatures quickly produce more thermally tolerant larvae. These studies underscore the ability of corals and anemones to persist under variable conditions. Nevertheless, a compelling effort to reduce rates of warming will be imperative to the survival of key ecosystems such as coral reefs.